1. Field of the Invention
This invention relates to the field of automatic power transmissions and in particular to such transmissions having multiple countershafts driven by multiple input shafts that are connected to a power source through multiple friction clutches.
2. Description of the Prior Art
Automatic transmissions usually require a hydraulic torque converter or fluid coupling located between the engine and the gear arrangement. These devices require a continuously pressurized hydraulic system and operate at fairly low efficiency over a great portion of their operating range. A preferred automatic transmission would eliminate the torque converter or hydraulic coupling and require only a small oil pump to pressurize a much smaller capacity hydraulic system for operating the clutches and servos that engage the several speed ratios.
It is necessary that an automatic transmission, particularly one for use in a vehicle wherein the engine and transmission are transversely mounted, have a small package space especially with regard to its overall dimension in the transverse direction. Preferably an automatic transmission would permit several aligned and coaxial input shafts to cooperate telescopically one within the other and in this way reduce the length of the transmission between the drivewheels of the vehicle. The length of the transmission can be minimized further if the number of gear wheels carried by the input shafts and countershafts is minimized for a given number of speed ratios.
Transmissions of the multiple countershaft type frequently have a reverse output gear wheel machined on the outer contour of the synchronizer clutch and a sliding gear reverse idler that is moved axially on a support shaft into engagement with a reverse pinion and the reverse output gear. If the reverse drive torque delivery path could be produced without the need for the additional support shaft and reverse idler, a more compact multiple speed ratio automatic transmission would result.